New ab initio potential energy surface for BrH2 and rate constants for the H plus HBr → H2 + Br abstraction reaction

A global potential energy surface (PES) for the electronic ground state of the BrH2 system was constructed based on the multireference configuration interaction (MRCI) method including the Davidson's correction using a large basis set. In addition, the spin-orbit correction were computed using the Breit-Pauli Hamiltonian and the unperturbed MRCI wavefunctions in the Br + H-2 channel and the transition state region. Adding the correction to the ground state potential, the lowest spin-orbit correlated adiabatic potential was obtained. The characters of the new potential are discussed. Accurate initial state specified rate constants for the H + HBr --> H-2 + Br abstraction reaction were calculated using a time-dependent wave packet method. The predicted rate constants were found to be in excellent agreement with the available experimental values and much better than those obtained from a previous PES. (C) 2011 American Institute of Physics. [doi:10.1063/1.3563750]